Zedora registration was based on studies of women with metastatic breast cancer, but its approval includes adjuvant treatment. Thus, prospective data of drug use in localized disease are lacking, as well as are real-world safety and efficacy data, taking into consideration comorbidities and compliance difficulties.

This will be an observational study of patients receiving adjuvant Zedora at several Brazilian institutions for the purpose of describing its efficacy and safety.

An observational, multicenter, prospective, real-world study at Brazilian institutions.

Adult patients with early HER2+ breast cancer receiving adjuvant biosimilar trastuzumab (Zedora) at the participating sites after the start of the study and meeting the eligibility criteria will be invited to participate. Demographics, comorbidities, disease history, extent of exposure to biosimilar trastuzumab (Zedora), adverse events and LVEF values will be collected.

Data collection will be performed using a case report form (CRF) specifically designed for the study.

Study Treatment:

Biosimilar trastuzumab (Zedora) must be prescribed at the dosage described in the product label.

Treatment duration will be 12 months for patients starting upfront with biosimilar trastuzumab (Zedora). Patients switching at any time to biosimilar trastuzumab (Zedora) after a period of adjuvant or neoadjuvant Herceptin® use will also be included in the overall analysis and subsequently assessed in a subgroup analysis.

Sample Size:

Number of patients = 170 Given the inexistence of a specific hypothesis to be tested, the statistical analysis will be basically descriptive.

Sample size is based on the two-sided 95% confidence interval (95% CI) for the invasive disease relapse-free survival rate.

The table below shows the 95% CIs for different rates in a sample of 170 patients, with an interval size ranging between 9% and 15%.

Based on literature, a 3-year relapse-free survival between 88 and 96% is expected. According to the table above, a sample of 170 patients allows assessing this endpoint with +/- 6.0% accuracy.

Study duration:

The estimated time for patient enrollment in the study is one year and may be extended in case the sample size is not reached in this period. Biosimilar trastuzumab (Zedora) must be prescribed according to the product label and treatment duration will be up to one year. The patient will be maintained in the study for 5 years (from start of treatment), unless there is tumor recurrence (local or distant).

Inclusion Criteria:

• female patients aged 18 years and over
• diagnosis of early stage I to III breast cancer confirmed by histopathology test according to local guidelines.
• human epidermal growth factor receptor 2 (HER2)-positive tumor by immunohistochemistry or FISH (Fluorescence In Situ Hybridization), as per the 2018 ASCO assessment guideline [J Clin Oncol 36:2105, 2018].
• use of at least one dose of biosimilar trastuzumab (Zedora) as adjuvant therapy, regardless of previous neoadjuvant trastuzumab or Zedora use or the type of chemotherapy combined with the antibody.
• Signing of the informed consent form (ICF).

Exclusion Criteria:

• use of biosimilar trastuzumab (Zedora) differently from the provisions in the label.
• patients enrolled in and followed up by Programa Vida Plena [Full Life Program].

Adult female patients with diagnosis of early stage I to III HER2+ breast cancer confirmed by histopathology test, immunohistochemistry test and FISH, where required, according to local guidelines, and who have started biosimilar trastuzumab (Zedora) as neoadjuvant or adjuvant therapy according to the product label will be eligible for the study.